In general, as shown in FIG. 1, an air conditioner system for a vehicle has a refrigeration cycle that includes: a compressor 1 for compressing and discharging refrigerant; a condenser 2 for condensing the refrigerant of high pressure discharged from the compressor 1; an expansion valve 3 for throttling the refrigerant condensed and liquefied in the condenser 2; and an evaporator 4 for exchanging heat between the liquefied refrigerant of low pressure throttled by the expansion valve 3 and air blown to the interior of the vehicle and evaporating the refrigerant to cool the air discharged to the interior of the vehicle due to heat absorption by evaporative latent heat, and that the compressor 1, the condenser 2, the expansion valve 3 and the evaporator 4 are connected with each other via refrigeration pipes. The air conditioner system cools the interior of the vehicle through the following refrigerant circulation process.
When a cooling switch (not shown) of the air conditioner system is turned on, first, the compressor 1 inhales and compresses gas-phase refrigerant of low-temperature and low-pressure while driving by driving power of an engine or a motor, and then sends the refrigerant in the gaseous phase of high-temperature and high-pressure to the condenser 2. Then, the condenser 2 condenses the gas-phase refrigerant into liquid-phase refrigerant of high-temperature and high-pressure by exchanging heat with outdoor air. After that, the liquid-phase refrigerant of high-temperature and high-pressure sent from the condenser 2 rapidly expands by a throttling action of the expansion valve 3 and is sent to the evaporator 4 in a wet-saturated state of low-temperature and low-pressure. The evaporator 4 exchanges heat between the refrigerant and air blown to the interior of the vehicle by a blower (not shown). Then, the refrigerant is evaporated in the evaporator 4 and discharged in a gaseous phase of low-temperature and low-pressure. After that, the gas-phase refrigerant is inhaled into the compressor 1, and then, recirculates the refrigeration cycle as described above.
In the refrigerant circulation process, as described above, the air blown by the blower (not shown) is cooled by evaporative latent heat of the liquid-phase refrigerant circulating inside the evaporator 4 and discharged to the interior of the vehicle in a cooled state so as to cool the interior of the vehicle.
Recently, in order to enhance cooling performance, a water-cooled condenser 20 and an internal heat exchanger 25 are applied to an air conditioner system. Referring to FIG. 2, the water-cooled condenser 20 heat-exchanges the refrigerant discharged to the compressor 1 with coolant to condense the refrigerant.
That is, coolant circulating inside a water-cooled radiator 50 mounted in an engine room of the vehicle is supplied into the water-cooled condenser 20 and exchanges heat with the gas-phase refrigerant discharged from the compressor 1, so that the gas-phase refrigerant is cooled and condensed to be changed into a liquid-phase refrigerant.
Moreover, the internal heat exchanger 25 which exchanges heat between the refrigerant discharged from the water-cooled condenser 20 and the refrigerant discharged from the evaporator 4 is mounted.
Therefore, the refrigerant discharged from the water-cooled condenser 20 enhances cooling performance through supercooling because being further cooled in the internal heat exchanger 25 and flowing to the expansion valve 3.
However, in the conventional air conditioner system, when the vehicle idles or when the outdoor temperature rises, temperature of the coolant passing the water-cooled radiator 50 also rises. In this instance, when temperature of the coolant rises, temperature of the refrigerant of the water-cooled condenser 20 which exchanges heat with coolant also rises. Thus, the refrigerant flows into the internal heat exchanger 25, and then, flows into the expansion valve 3 and the evaporator 4 to cause deterioration in cooling performance.
Furthermore, the refrigerant discharged from the evaporator 4 flows into the internal heat exchanger 25, and then, flows into the compressor 1 after exchanging heat with the refrigerant with elevated temperature. Thus, temperature of the discharged refrigerant of the compressor 1 rises above an upper limit, so that durability and stability of the air conditioner system are deteriorated, for instance, the refrigerant leaks or lifespan of the air conditioner system decreases.
Referring to FIG. 13, you can see that temperature of the refrigerant discharged from the compressor 1 rose above the limit, and temperature of the refrigerant which flew into the compressor 1 and temperature of the refrigerant which was discharged from the water-cooled condenser 20 also rose higher than temperature of the present invention.